The present invention relates to structural bearings.

The invention provides a structural bearing comprising: a lower non-elastomeric load-bearing element; an upper non-elastomeric load-bearing element; and at least one load-bearing intermediate element interposed between the upper and lower non-elastomeric elements; and wherein: the upper and lower non-elastomeric elements are rotatable relative to each other at least to a limited extent about a vertical axis; the intermediate element or one of the intermediate elements is an elastomeric element unconfined at its periphery; and the upper and lower non-elastomeric elements are provided with respective lateral or side surfaces which are mutually engageable to restrict relative lateral movement of the upper and lower non-elastomeric load-bearing elements while allowing the upper and lower non-elastomeric elements to rotate relative to each other about the vertical axis.

Preferably the side surfaces of the upper and lower non-elastomeric load-bearing elements extend completely around the axis, each surface constituting a complete respective surface of revolution. I.e. preferably the side surfaces are annular. Alternatively each side surface may be comprised of one or more arcs of such a surface of revolution.

Preferably the intermediate element or one of the intermediate elements and one of said upper and lower non-elastomeric load-bearing elements are provided with respective mutually engaging and relatively slidable surfaces extending about the vertical axis whereby the intermediate element or said one intermediate elements and the other of said non-elastomeric elements can rotate in relation to said one non-elastomeric element about the vertical axis, said one non-elastomeric element and the

intermediate element or said one intermediate element sliding one upon the other.

Alternatively the upper and lower non-elastomeric elements may be rotatable to a limited extent relative to each other about the vertical axis by virtue of torsional compliance within the elastomeric element or at least one of the elastomeric elements, the upper and lower non-elastomeric elements and intermediate element or intermediate elements being frictionally engaged with each other at their respective adjacent surfaces or otherwise held first to each other at their respective adjacent surfaces so that relative sliding movement between the elements does not occur.

It is to be understood that the term "vertical" in relation to the axis is used for convenience of description. In practice, in use of the bearing of the invention, it is possible for the axis to be inclined somewhat from the vertical or even to be horizontal.

Preferably the elastomeric element is circular in plan and concentric with the vertical axis. To ir-aximize the vertical load carrying capacity of the bearing the elastomeric element should be of the maxirπum possible diameter consistent with its being unconfined at its periphery.

Preferably the upper and lower non-elastαreric load-bearing elements are circular in plan and concentric with the vertical axis.

It will be appreciated that such circular non-elastomeric elements may be economically and precisely manufactured by turning.

Preferably the at least one intermediate element is circular in plan and concentric with the vertical axis.

The elastomeric element is preferably located in a recess in one of the upper and lower non-elastomeric load-bearing elements.

The side surfaces of the upper and lower non-elastomeric load-bearing elements, which may be referred to as "mating surfaces", are preferably cylindrical.

The side surfaces or surfaces of revolution preferably have a diameter which can circumscribe the elastomeric element. This enables the engageable or mating surface area of the side surfaces of the upper and lower non-elastomeric load-bearing elements to be optimized for lateral load carrying capacity.

By providing the side surfaces of the upper and lower non-elastcmeric local bearing elements substantially level with the elastomeric element or elements the bearing may advantageously be made of a low height, i.e. the bearing may be made compact in the vertical direction.

The side surfaces may be in sliding contact with each other over their entire circumferential extent whereby relative lateral movement between the upper and lower non-elastomeric load-bearing elements is precluded (except to the extent allowed by the compliance of the materials providing the surfaces of revolution) . The respective surfaces of revolution are in this case substantially coincident.

Alternatively the side surfaces of the upper and lower non-elastcmeric load-bearing elements may be spaced apart to allow limited relative lateral movement between the upper and lower non-elastomeric load-bearing elements.

At least one of the side surfaces of the upper and lower non-elastomeric load-bearing elements may be provided by a cylindrical wall forming part of the one of the upper and lower non-elastomeric load-bearing elements. Cylindrical walls are ideal structural forms for transferring lateral loads between the upper and lower elements and because of this can be made thin.

The aforementioned recess accommodating the elastomeric element may be defined within such a cylindrical wall, one of the surfaces of revolution being provided at the outside of the cylindrical wall.

Preferably the external peripheral surfaces of the bearings are circular in plan. Such surfaces, whether formed by casting, forging or machining may impart a pleasing appearance to the bearing.

The upper non-elastomeric element may be capable of tilting relative to the lower non-elastomeric element about a horizontal axis to an extent limited by the initial clearance between the engageable side surfaces of the upper and lower non-elastcmeric elements and/or by the compliance of facing materials providing the side surfaces.

The required stiffness of tilting, until the limit is reached, may be obtained by adopting appropriate dimensions and composition of the elastomeric element.

The elastomeric element or elastomeric elements may be provided with reinforcing plates of e.g. steel.

The dimensions and compositions of the elastomeric element or elements can be adapted to provide required stiffness properties under vertical, tilting and, where required, pivotal forces and lateral shear forces.

The elastomeric element may have different arrangements of steel reinforcing plates to achieve the required stiffness properties. The external dimensions may be varied as desired and further variations may be achieved by mating the elastomeric hollow in its central region around the vertical axis.

The bearing may comprise connection means between the upper and lower non-elastomeric elements to prevent their separation along

the vertical axis, and/or to preload these elements and the intermediate element or elements and/or to transmit uplift or upward vertical loading from the upper non-elastomeric element to the lower non-elastcmeric element and the lower structure.

Preferably the connection means takes the form of a central pin or bolt.

The invention is further described below by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a plan view of a first structural bearing according to the invention;

Figure 2 is side view, partly in section, of the first structural bearing;

Figure 3 is a plan view of a second structural bearing according to the invention;

Figure 4 is a side view, partly in section, of the second structural bearing;

Figure 5 is a plan view of a third structural bearing according to the invention;

Figure 6 is a side view, partly in section , of the third structural bearing; and

Figure 7 is a sectional view of part of a fourth structural bearing according to the invention.

In the drawings like reference numerals indicate similar, but not necessarily identical, parts.

Referring to Figures 1 and 2, the first structural bearing 1

comprises a lower metal load-bearing element 2, an upper metal load-bearing element 3 and an elastomeric element 4 disposed between the elements 2 and 3.

The elements 2, 3 and 4 are each circular in plan and concentric with a vertical axis X.

The element 2 has a central through hole and is formed with an upstanding circular wall 5 inset from its circumference or outer periphery. The elastomeric element 4 is located in the recess defined by the wall 5. A clearance is defined between the periphery of the element 4 and the wall 5 so that the periphery of the element is unconfined. The outer surface of the wall 5 is provided with a sheet or band 6 of stainless steel in the form of a ring, the radially outer surface of which is polished.

The elastomeric element 4 is in the form of a nodule with a central through hole. The module is laminated with steel plates 7. To the upper surface of the element 4 is fixed fast a layer 8 of polytetrafluoroethylene (P.T.F.E.).

The element 3 has a central through hole with an enlarged upper portion and is formed with a depending circular wall 10 at its circumference or outer periphery. Within the recess defined by the wall 10 the wall 5 of the element 2 is accoππ dated.

To the lower surface of the element 3, within the wall 10, is fixed fast a sheet of stainless steel sheet 11, the lower surface of which is polished.

To the inner surface of the wall 10 is fixed fast a layer of P.T.F.E. forming a band or ring 12.

An uplift restraining pin 13 is located in the central holes of the elements 2, 3 and 4, the head of the pin being accommodated in the enlarged upper portion of the hole in the element 3 and the shank

of the pin being screw-threadedly engaged in the hole of the element 2 and tack welded to the element 2. The pin 13 serves to preload the bearing and to prevent the elements 2, 3 and 4 separating from each other before and during use of the bearing. Sub- stantially no clearance is left between the head of the pin 13 and the element 3 and between the unthreaded part of the shank of the pin and the elements 3 and 4.

It will be understood that the radially outer side surface of the band 6 of stainless steel and the radially inner side surface of the P.T.F.E. ring 12 are surfaces of revolution, specifically cylindrical surfaces, centered on the axis X.

In use of the bearing, the bearing is located between two structural members or parts, specifically a lower load-bearing structural member and an upper structural member which imposes a load on the bearing and may be fixed fast to these structural members. The upper structural member and the upper element 3 can rotate about the vertical axis X relative to the lower element 2 and and the lower structural member, the stainless steel sheet 11 sliding on the P.T.F.E. layer 8 and the P.T.F.E. ring 12 sliding on the stainless steel ring 6.

Downward vertical load is transmitted from the upper structural member through the element 3, the stainless steel sheet 11, the P.T.F.E. layer 8, the element 4 and the element 2 to the lower structural member. Upward vertical load is transmitted from the upper structural member through the element 3, the pin 13 and the element 2 to the lower structural member.

Lateral forces are resisted by the wall 10 of the member 3 acting on the member 2 through the P.T.F.E. ring 12 and the stainless steel ring 6.

The bearings shown in Figures 3, 4, 5, 6 and 7 are similar, in construction and use, to the bearing shown in Figures 1 and 2,

except as described below.

Referring to Figures 3 and 4, the bearing shown therein includes a further upper metal element 20.

The element 3 has a central, upwardly open recess and the element 20 has a protuberance engaging in the recess.

The recess of the element 3 has straight inwardly facing parallel side surfaces 3* . Similarly the protruberance of the element 20 has straight outwardly facing parallel side surfaces 20' .

To the upper surface of the element 3, within the recess of the element, is fixed fast a P.T.F.E. sheet 21. To the inwardly facing side surfaces 3' of the element 3 are similarly fixed strips 22.

The lower surface of the protruberance of the element 20 is provided with a stainless steel sheet 23, the lower surface of which is polished. Similarly the outwardly facing side surfaces of the protruberance are each provided with a stainless steel sheet 24, the outer surfaces of which are polished.

The element 20 has a generally elongate central through hole parallel with the side surfaces 3" and 20' and with an enlarged upper portion. The pin 13 is located with its head in the enlarged upper portion of the hole and passes through the holes of the elements 20, 3, 4 and 2 as in Figures 1 and 2, and is screw threadedly engaged with the element 2 to preload the bearing and then tack welded to the element 2.

In use of the bearing, the upper structural member and element 20 are displaceable in one horizontal direction relative to the lower structural member and the lower element 2, the stainless steel sheets 23, and 24 sliding on the P.T.F.E. layer 21 and the P.T.F.E. layers or strips 22 respectively. Such horizontal displacement is limited by engagement of the pin 13 with the ends of the hole in

the element 20.

Referring to Figures 5 and 6, to the element 3 is attached by bolts or screws 30 a circularly syrtmetrical metal element 31 having a vertical wall portion 31' and a horizontal portion 31' ' defining a 5 space in which is held captive a metal element 32. The upper surface of the element 3 is provided with a stainless steel sheet 33, the upper surface of which is polished. To the lower surface of the element 32 is fixed fast a P.T.F.E. layer 34.

To the upper part of the element 32 is fixed by bolts 35 a thick 10 metal load-bearing plate 36.

An annular space 38 is defined between the circumference of the element 32 and the vertical portion 31' of the element 31. Also a recess is defined in the lower surface of the element 32 surrounding a portion of the head of the pin 13 which protrudes 15 above the element 3.

In use of the bearing, the upper structural member rests on the plate 36. The upper structural member, the load-bearing plate 36 and the member 32 can move in any horizontal direction within limits defined by engagement of the circumference of the member 32 20 with the wall portion 31' of the element 30.

Referring to Figure 7, the fourth bearing 40 comprises a lower metal load-bearing element 42, an upper metal load-bearing element 43, an elastomeric element 44 disposed between the elements 42 and 43, a stainless steel plate 45 the underside of which is polished, 25 disposed between the element 44 and the element 42 and a thick metal plate 46 disposed in a recess in the underside of the element 42.

The elements 42, 43, 44, 45 and 46 are each circularly syrrmetrical. A bolt or pin 48 extends centrally through the elements 42, 43, 44, 30 45 and 46.

The element 42 is formed with a horizontal peripheral flange portion 42' and a central upwardly projecting boss 42' ' . The above-mentioned recess in the underside of the element 42 is disposed beneath the boss 42" .

The boss 42' ' has a central hole through which the shank of the pin 48 passes, a substantial clearance 50 being defined between the shank and the side surface of the hole.

To the upper surface of the boss 42' ' is fixed fast a layer 49 of P.T.F.E.. The element 44 is circularly syπτretrical and has a central hole through which the shank of the pin 48 passes with substantially no clearance.

The element 43 has a central through hole with an enlarged upper portion and is formed with a depending circular wall 52 at its circumference or outer periphery. Within the recess defined by the wall 52 the elements 44, 45 and the boss 42' ' are located.

The head of the pin 48 is located with substantially no clearance in the enlarged upper portion of the central hole of the element 43 and is tack welded to the element 43. The shank of the pin extends through the remainder of the hole with substantially no clearance.

The elastomeric element 44 is in the form of a module with a central hole. The module is laminated with steel plates 54. The shank of the pin 48 passes through the central hole with substantially no clearance.

The metal plates 46 and 49 also each have a central through hole. The shank of the pin 48 passes through the holes with substantially no clearance.

A layer of P.T.F.E. 55 is fixed fast to the underside of the boss 42".

To the upper surface of the element 46 is fixed fast a stainless steel sheet 56.

The shank of the pin 48 is unthreaded, except at its lower end, onto which is screwed a nut 58, the pin together with the nut 5 serving to prevent the elements 43 to 46 separating from each other before use and during use of the bearing, to preload the bearing andnto transmit upward vetical forces applied to the element 43. A washer 59 is disposed between the bolt 58 and the element 46.

To the underside of the element 42 is bolted a part-spherical cover 10 60 which protects the nut 58 and the recess in the lower side of the element 42 from penetration of mortar when the bearing is installed.

A water outlet 62 extends from the lowest part of the interior of the cover 60.

15 Height adjusting screws 64 are screw-threadedly engaged in the flange 42' of the element 42.

In use of the bearing, the bearing is located on a mortar bed 100 on a lower structural member or part 101. The structural part 101 is provided in its upper surface with a recess to receive the cover 20 60 and is also provided with a drain 102. A flexible conduit 104 is connected with the outlet 62 of the cover and arranged to extend through the drain 102.

The desired spacing between the part 101 and the element 42 may be predetermined by adjustment of the screws 64. An upper structural 5 member or part (not shown) is located on the element 43.

The upper structural member imposes a load on the bearing.

The upper structural member can rotate about the vertical axis of the pin 48 relative to the element 42 and the lower structural

member 101, the stainless steel plate 45 sliding on the P.T.F.E. layer 49 and the stainless steel sheet 56 sliding on the P.T.F.E. layer 55.

Downward vertical load is transmitted from the upper structural member through the element 43, the elastomeric element 44, the element 49 and the element 42 to the lower structural member 101. Upward vertical load is transmitted through the element 43, the pin 48, the nut 58, the plate 46 and the element 42 to the lower structural member 101.

The upper structural member and the element 43 are displaceable in any horizontal direction relative to the lower structural member 101 and the element 42, the stainless steel plate 45 sliding on the P.T.F.E. layer 49 and the stainless steel sheet 56 sliding on the P.T.F.E. layer 54. Such horizontal displacement is limited by the wall 52 of the element 43 engaging with the outer circumferential surface of the boss 42' ' .

Water or other liquid which may penetrate into the bearing may drain away through the outlet 62.

It will be understood that in each of the bearings described above relative sliding movement between elements is provided by the provision of a polished stainless steel surface and a P.T.F.E. layer which slide upon each other. In each particular case, the stainless steel member providing the stainless steel surface and the P.T.F.E. layer may be reversed.

The metal elements which are not of stainless steel may be of mild steel.